Telephone-exchange system



June 30, 1925.

i.. H. JOHNSON TELEPHONE EXCHANGE SYSTEM June 30, 1925. 1,543,854

. L. H. JOHNSON TELEPHONE EXCHANGE SYSTEM Filed Jan. 3, 1921 2 Sheets-Sheet 2 mn Q E5 l: N NNUU wmmmlm 1,234,169.12 13,14, l5. 5|?, le

e w/S Udo/m505.

y mM/Wy lil() Patented .lune 30, i925..

ATES

LEWS H. JOHNSON, OF BLOOIVIFIELD, NEVI JERSEY, ASSIGNOB- TO' WESTERN ELEO- TRIO COlVIPANY, NCORPORATED, Oli' NE'W YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHOlJE-EXCEANGE SYSTEM.

Application filed January To ZZ air/0m t may concern:

Be it known that I, Lnwrs H. JOHNSON, a citizen of United States, residing at Bloomlield, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

his invention relates to a telephone exchange system and more particularly to a system in which connections are established by machine switching equipment.

ln systems in which the control of automatic switches is effected by a central otlice sending` mechanism through the transmission of revertive impulses from the switches to the sending mechanism, it is essential that the operations of the switching mechanism and oliice sending mechanism be kept in synchronism, in order that the switches shall be positioned accurately in accordance with the line designation which has been set up at the sender by the Calling subscriber or operator. ln such systems local district selece tors are employed to extend connections to the proper district or office of the exchange and incoming and final selectors are employed in each district or oilice to further extend the connections to the terminals of the desired lines.

ln accordance with the usual practice the incon'iing selector is controlled by a control relay which is connected directly into the interol'lice trunk circuit extending back to the district selector, the trunk circuit forming part of a closed loop circuit, commonly known as the fundamental circuit, extend ing in the wcll known manner through the winding` of the stepping or control relay of the sending mechanism. During the advance of the selector switch the stepping relay of the sender is operated by pulses transmitted to it over the fundamental circuit by the eommutator of the switch until the sender is satisfied with respect to .its particular setting, when the 'fundamental circuit is opened at the sender to render the control relay of the switch currentless whereby the advance of the switch is ar` rested. It is therefore apparent that the control relay of theA switch must release immediately upon the satisfaction of the sender or upon the opening of the fundamental circuit at the sender, in order that the switch shall not overrun and thus position its brushes upon the wrong group or set of terminals.

lVhere the districts or offices of the exchange are located adjacent each other o1* not exceeding twelve or thirteen miles apart, the control relay of the switch functions quickly enough to provide accurate operation of the switch. If, however, the interotlice trunk comprises a cable of greater length, the control relay, by reason of the capacity charge upon the cable, has a tendency to release more slowly following the opening of the fundamental circuit at the sender. The interval between circuit opening at the sender and the release of the control relay of the switch, during operation over a cable thirty miles in length is substantially increased to three times the interval obtaining duringoperation over a cable two miles in length, which, added to the usual delay in arresting the movement of the switch, sulticicnt to enable the switch shaft to advance the brushes beyond the de` si red position. This tendency of the switch to overrun is more apparent during the group selection movement of incoming selector and also since the final selector must be operated over approximately the same length of cable, applies equally well to the selective operation of the final selector switch.

It is, therefore, the object of this invention to enable the accurate control of selector switches over long interotlice cable loops.

More specilically it is an object of this invention to provide special controlling circuits for an incoming selector switch and to provide for repeating revertive impulses from a iinal selector switch to the oiiice sending mechanism.

(lne feature of the invention resides in the provision of a sensitive line relay at the incoming selector switch adapted to be controlled over the interotlice trunk and which in turn controls the circuit of the usual control rclay ot the switch, and in the provision of a special commutator for governing the control relay of the switch and for transrevertive impulses to the otlice sender.

A further feature of the invention relates to the provision of means comprising a polarized relay at the incoming selector switch for repeating revertive pulses transmitted from the commutator of the inal selector switch to the office sender and for rendering the line relay of the incoming selector sensitive to the opening of the fundamental circuit at the sender.

Such other features of the invention as are contemplated by the present invention will become more apparent from the following description and the appended claims.

The invention will now be described in connection with the accompanying drawings which disclose one specific embodiment of the invention. In the drawings, Fig. 1 shows the line of a calling subscriber, a diagrammatic illustration or' a subscribers individual line switch, a district selector, oliice sender, and so much of the circuits of the incoming selector switch as is necessary to disclose the present invention; and Fig. 2 shows the circuits or' a final selector switch and the line of a called subscriber.

Inasinuch as the manner in which a connection is extended from the calling subscribers line to the incoming selector switch, is not essential to an understanding of this invention, the circuits of the subscribers line switch, district selector switch and oiiice sender have been disclosed only diagrammatically. For a full disclosure of these circuits and the manner in which they function, reference may be had to the patent to F. A. Stearn and F. J. Scudder, No. 1,395,977, issued November 1, 1921.

The incoming selector switch shown in Fig. 1 and the final selector switch shown in Fig. 2 are of substantially the same type as disclosed in the aforesaid patent, being modified however for the purposes of this invention.

rl`he manner in which the system is organf ized will best be presented in connection with a description of the mode of its operation.

It will be assumed that the calling subscriber at station A desires to establish a connection with the line of subscriber B which line is located at a distant ollice o'l the exchange. To initiate the call, the calling subscriber removes his receiver from the switch-hook whereupon the individual line switch functions in the well known man- 'ner to extend a connection from the calling tending to the particular olice of the eX- change in which the line of the desired sub scriber terminates.

Upon the extension of the connection to the interoiiice trunk 103, which terminates in an incoming selector switch 104, the se quence switch (not shown), associated with the district selector, advances into position 10 and a fundamental circuit is established extending from the oliice sender 102 which may be traced from battery, through the lower contact of cam 105, resistance element- 133, the left-hand winding of line relay 106, the left-hand Contact of cam 107 (1 to 8), the tip conductor of theV interotiice trunk 103, bank terminal 108, and brush 109 of the district selector switch, the right-hand contacts of cam 110 associated with the sequence switch of the district selector, conductor 111, the armature and back contact of the 0 counting relay 112 of the otce sender, the contact of cani 113 associated with the seH quence switch (not shown) of the oli'ice sender, the windings of the sender stepping relay 114, conductor 115, the lower left-hand and upper right-hand contacts of cam 116 associated with the sequence switch of the district selector, brush 117, and bank terminal 118 of the district selector switch, the lower right-hand contact of cam 119 (17 to 8), and thence to ground at the right-hand contacts or cam 120 (9 to 7).

The sender stepping relay 11/1- and the line relay 10G of the incoming selector switch energize in this circuit, the sender stepping relay preparing a circuit in the well known manner for counting relays of the sender and the line relay 106 or' the incoming selector, closing a circuit for the control relay 121 of the incoming selector. The circuit ot' relay 121 may be traced from battery, through the lett-hand winding of this relay, the lower right-hand and upper lefthand contacts of cam 122, the armature and front Contact of relay 106, and thence to ground at the lower right-hand contact ol cam 120. Relay 121 upon energizing in this circuit, closes a circuit for advancing sequence switch 123 out of position 1 and under the influence orl master cam 121:, into position 2. This circuit may be traced from battery, through the magnet winding ot sequence switch 123, the lower contact ot' cam 125 (1), and thence to ground through the left-hand armature and front Contact ot relay 121. As soon as sequence switch 123 leaves position 1, the initial energizing circuit oli relay 121 is opened at the lower right-hand contact of cam 122, and a holding circuit is established for relay 121, which may be traced from battery, through its left-hand winding, the contacts of cam 120 (17 to 11), the right-hand armature and front contact of relay 121, the upper contacts oi cam 122, the armature and front contact of relay 106, and thence to ground at the lower right-hand contact of cam 120 (9 to 7).

lVith sequence switch 123 in position 2 and relay 121 energized, a circuit is established tor the up-drive magnet 127 which may be traced from b-attery, through the winding o't magnet 127, the lower contacts ot cam 12S, and thence to ground at the leit'thand armature and front contact ot' relay 121. Under the influence of magnet 127, the depending portion of switch shaft 129 is pressed against the constantly rotating updrive drum 130 and the switch shaft is driven upwardly in its brush selecting movement.

As the switch shaft reaches its lirst brush selective position, the shaft wiper 131 engages a conducting portion of the eomnmtator segment 132, whereupon a circuit is established in shunt of the windings ot' the sender stepping relay 11st, which may be traced Yt'rom battery, through the lower contact ot cani 105, resistance element 133J the lett-hand winding ot line relay 106, the lower contact ot cam 107 (13/4 to 2), conductor Vi3-t, connnutator segment 132, shalt viper 131, the lett-hand contacts ot cam 128y and thence to ground at the lett-hand armature and liront contact of relay 121. 1n response to the establishment of this shunt circuit, the sender stepping relay 11-1 becomes deenergized and in the well known manner causes the energization ot one ot the counting relays ot the sender. Line relay 106 is, however, maintained energized over the shunt circuit. It is to be noted in this connection that commutator segment 132 is so placed with respect to the wiper 131, that the wiper 131 will engage a conducting portion ot the commutator segment at a period suiiiciently in advance ot the positioning oi the brushes ot the switch with relation to a set of bank terminals, and suliiciently in advance of the engagement ot holding pawl 135 with a notch in the de pending portion of the switch shatt 129, to insure that the switch shaft shall not overrun in case the fundamental circuit is opened at the sender at the time the shalt wiper 131 engages a conducting portion ol' the coxnniutator segment 132.

As the switch shaft 129 continues in its upward movement vthe wiper 131 engages an insulating portion ol' the segment 132, and the previously traced shunt circuit is opened whereupon the stepping relay of the sender again energizes and causes the circuits ot the sender to Function in the well known manner. 1n a similar manner as the. switch sha'tt 120 moves upwardly the sender stepping relay 11a is intermittently denergized and energized until the setting of the sender with respect to incoming brush selection is satisfied and the No. 0 counting relay 112 is energized to open the fundamental circuit.

Upon the opening of the fundamental circuit by the counting relay 112, the previously traced circuit, through the line relay 106 at the incoming selector, is opened and since the' left-hand energizing winding ot relay 106 is of low resistance, relay 106 deenergizes as soon as shaft wiper 131 engages the next insulating portion ot commutator segment 132. The provision ot the low resistance energizingl winding on relay 106 permits the cable capacity in the intcroil'iee trunk to charge very quickly through this winding, so that relay 106 is not rendered sluggish to deenergize by reason of such charge lirough its winding.

Upon the decnergization o't relay 106, the previously traced circuit tor relay 121 is opened at its armature and front contact and relay 121 inunediately deenergizes to open the circuit oli the up-drive magnet 127 to arrest the upward movement olf the switch sliait. At its lett-hand armature and back contact relay 121 closes a circuit -tor driving sequence switch 123 out ot position 2 and into position 3, this circuit extending from battery, through the magnet winding ol' sequence switch 123, the upper contact of cam (2), and thence to ground at the letthand armature and back contact ol relay 9 121.

)Vith sequence switch 123 in position 3v a circuit is established 'tor the trip magnet 136 which may be traced `from battery, through the winding oit this magnet, and thence to ground through the lower contacts o1 cam 137 (3 to The trip magnet 136i upon energizing, rotates the tripping spindie 13S to position a tripping tinger in association with the tripping cam (not shown) ot the selected set ot brushes preparatory to tripping the selected set of brushes upon a subsequent upward movement ol the switch Sllult.

As soon as the sequence switch reaches position 3, the previously traced Afundamental circuit is again established through the windings ot solider' stepping relay 111-, and the lett-hand winding ot line relay 106, and the previously traced energizing circuit ot relay 121. is again established through the lower right-hand contact ot cani 122 the upper lett-hand contact ot cam 122 (0 to Ll), and thence to ground at the lower right hand contact of cam 120, and relay 121 upon energizing establishes the previously traced circuit ttor advancing sequence switch 123 into position et. lilith sequence switch in position 4, the. previously traced locking circuit is established tor relay 121 and the circuit of the up-drive magnet 127 is again established.

Upon the energizaiion ot rip-drive magnet 12T` the switch sha'it is again driven pwardly in its group selection movement. l

As the selected set of brushes approaches its first group selection position, the shatt wiper 13S engages a conducting portion of the group selection commutator segment 139 and a circuit is established in shunt o't` the winding of sender stepping relay 11% which may be traced from battery, through the lower contact ot cam 105 (9 to L 1), resistance element 133, he left-hand winding ot relay 10G, the upper lett-hand contact of cam 107, (1 to 8) the upper contact of cam 110 (3% to Ll), conductor 141, commutator segment 139, shatt wiper 188, the left-hand contacts ot cam 12S, and thence to ground at the lett-hand armature and iront contact ot' relay 121. The sender stepping relay 111 being shunted, deencrgizes and functions in the well known manner, but line relay 100 is maintained energized over the shunt circuit. As the switch shaft continues in its upward movei'nent, the wiper 138 engages an insulating portion ot con'nnutator segment 139 and the previously traced shunt circuit is opened, whereupon the sender stepping relay 111 again energizes. 1n this manner as the switch shatt continues in its upward inovement the sender stepping relay 111 is intermittently deenergized and energized until the sender is satisfied with respect to its incoming' group selection setting or until the No. 0 counting relay 112 cnergizes to open the fundamental circuit.

As soon following the opening of the fundamental circuit as the shatt wiper 13S engages the next insulating portion ot the commutator segnient 139, line relay 100 becomes deenergized and opens at its armature and liront contact the circuit ot control relay 121. To insure that relay 121 shall not deenergize to arrest the upward movement of the switch sha'tt until the brushes have been properly centered upon the first set of terminals in the selectedY group, relay 121 is maintained energized over a locking circuit which may be traced from battery, through its right-hand winding, the lower right-hand and upper letthand contacts ot cani 1472, conductor 1413, conin'iutator segment 111, shai't wiper 115, the lett-hand contacts ot cani 12S, and thence to ground at the lett-hand armature and front contact ot relay 121. As soon ,as the selected set ot brushes has been prop` erly centered upon the lirst set of terminals in the selected group, wiper 115 will engage an insulating portion of the connnutator segment 111 and the maintaining circuit ot relay 121 will be opened whereupon relay 121 deenergizes, opening at its lett-hand armature and :trout contact the circuit ot updrive magnet 127 to arrest the upward movement of the switch shatt and closing at its lett-hand armature and back contact the previously traced circuit for advancing sequence switch 123 out of position 4 and into position 5.

It is to be noted that the commutator segment 139 is placed at such a distance in advance of shaft wiper 138 that the circuit of relay 106 will be opened early enough to insure that the switch shaft. shall not overrun in its selection movements and control relay 121 is maintained locked up over the centering segment 111e to insure that the switch shaft shall not underrun or become arrested in its movement betore the brushes reach the proper set ot bank terminals. lllith sequence switch 123 in position 5, a circuit is established ttor relay 121 which may be traced :trom battery, through the right-hand winding of relay 121, and thence to ground through the lower contacts ot cam 112. Relay 121 upon energizing closes a locking circuit for itself extending through its lett-hand winding, the contacts ofi cam 120, the right-hand armature and trent contact ol relay 121, the upper contacts ot cam 137, and thence through the test brush 158 and to the grounded test terminal 159 upon which it is then resting it Jthe first trunk ot the selected group is busy. At its lett-- hand armature and front contact, relay 121 closes a circuit tor advancing sequence switch 123 into position G and establishes the previously traced circuit extending through the winding ot the updrive niagnet 127.

Upon the energization ot magnet 12T, the switch shaft is driven upwardly in its trunk hunting movement until the test brush 158 engages the test terminal oit an idle trunk which it will be assumed is the trunk terminating in bank terminals 160, 161 and 102, when the previously traced locking circuit ot' relay 121 will be opened at test brush 158. Relay 121 is, however, maintained energized until the brushes are properl)Y centered upon the bank terminals 100, 101 and 162, over a circuit which may be traced from battery, through the right-hand winding of relay 121, through the lower right hand and upper lett-hand contacts o'l' cani 142, conductor 143, conm'mtator si-gnient 1111, wiper 115, the lett-hand contacts ol' cam 12S, and thence to ground at the letthand armature and front contactI o'l`A relay 121.

Relay 121 upon deenergizing` opens the circuit ot the up-drive magnet 127 to arrest the upward movement of the switch sli-att and at its lett-hand armature and back contact closes the previously traced circuit for advancing sequence switch 123 into position 7. lVith sequence switch 128 in position T. relay 121 is again energized over a circuit which may be traced through its left hand winding, the right-hand contacts of cam 122, and thence to ground through the letthand contacts ot cam 137. Relay 121 upon CIK energizing closes at its left-hand armature and front contact a circuit for advancing sequence switch 123 into position 8, and also closes a locking circuit for itself which may be traced t-hrough its lett-hand winding, the contact of cam 126, the right-hand armature and liront contact of relay 121, the lower right-hand contact of cam 146 (6% to 18), brush 147 and bank terminal 161. con ductor 14S, the upper left-hand and lower right hand contacts of cam 200, resistance element 201, and thence to ground through the lower left-hand contact of cam 202 (1 to 8%). Relay 121 is maintained energized over this circuit until the sequence switch 203 of the final selector 250 advances out of position 8%, following the completion of the units selection movement of the linal selector switch.

Vit-h sequence switch 123 in position 8, the 'fundamental circuit is again established between the office sender and the line relay 106 of the incoming selector. The fundamental circuit may now be traced from battery, through the upper contact of cam 105 (7 to 8), the left-hand winding of relay 106, the upper left-hand Contact of cam 107 (1 to 8), bank terminal 108. and thence as previously traced through the oliice sender, returning through bank terminal 118, the lower right-hand contact of cam 119 (17 to 8) and thence to ground through the armature and back contact of relay 151.

Sender stepping relay 114 and line relay 106 energize in this circuit, line relay 106 establishing a circuit for the line relay 204 of the final selector switch, which circuit may be traced from battery, through the' left-hand contact of cam 205 (1 to 10), the right-hand winding of relay 204, the lower lett-hand contact of cam 206 (1), the lower left-hand contact of cam 207 (15 to 6), trunk conductor 208, bank terminal 162 and brush 149 of the incoming selector switch, the right-hand contact of cam 150 (8), the armature and front Contact of line relay 106, the left-hand contact of cam 120 (8) the winding of polarized relay 151 and thence to grounded battery. It is to be noted that this circuit extends from battery to battery through the windings of relays 151 and 204. but the battery connected to the Winding of relay 151 is of lower potential than the battery connected to the winding of relay 204, and therefore suiiicient current flows over the circuit to cause the energization of relay 204. Relay 151, however, being polarized does not energize in this circuit to move its armature from its back contact.

Relay 204 upon energizing establishes a circuit tor relay 209 which may be traced from battery, through the left-hand winding of relay 209, the upper lett-hand contact of cam 210, the left-hand armature and front contact of relay 204, and thence to ground at the upper contact of cam 211. Relay 209 upon energizing establishes a circuit for advancing sequence switch 203 out of position 1 and under the influence of master cam 212 into position 2. This circuit may be traced from battery, through the magnet winding ot sequence switch 203, the lower contacts of cam 218, and thence to ground at the righthand armature and front contact of relay 209.

Relay 209 also establishes a locking circuit tor itself extending through its lefthand winding, the armature and back contact ot relay 214, the left-hand armature and trout contact of relay 209, thence over sleeve conductor 215, bank terminal 160 brush 159. and to ground through the upper right-hand and lower left-hand contacts of cam 137.

With sequence switch 203 in position 2 and relay 204 energized, acircuit is established tor the high speed up-drive magnet 216 which may be traced from battery, through the winding of magnet 216, the lower contact of cam 217, (2) the left-hand armature and front Contact of relay 204, and thence to ground at the upper contact of cam 211. In response to the energization of magnet 216, the depending portion of switch shaft 21S is pressed against the constantly rotating 11p-drive drum 219 and and the switch shaft is moved upwardly in its brush-selecting movement. As the switch shaft approaches its rst brush selection position, the shaft wiper 220 engages a conducting portion of the commutator segment 221 and a circuit is established for effectively energizing the polarized relay 151 which may be traced from battery, through'the winding of relay 151, the lower left-hand contact of cam 120 (8), the armature and front contact of relay 106, the right-hand contact of cam 150, brush 149, and bank terminal 162, trunk conductor 208, the lower lett-hand and upper right-hand contacts of cam 207, conductor 223, commutator segment 221, wiper 220 and thence to ground through the upper lett-hand contact of cam 202.

Relay 151 upon attracting its armature opens a shunt normally connected around the intermediate high resistance winding of line relay 106. which shunt may be traced through the intermediate winding ot relay 106, the lower contacts of cam 119, and thence to ground at the armature and back contact ot relay 151, and closed at the front contact of its armature a circuit for including the right-hand high resistance differential winding of relay 106 in series with the intermediate winding of the relay. This series circuit may betraced from battery, through the upper contact ot' cam 105, the right-hand winding` ot relay 106, the armature and front contact of relay 151, lower contacts of cam 119, and thence to ground through the intermediate winding of relay 106. Upon the removal of the shunt from around the intermediate winding o't` relay 106, this high resistance winding is ellectively connected into the fundamental circuit whereupon the current flowing over the tundamental circuit is reduced to such an extent that sender stepping relay 1 1-1- deenergizes.

As the switch shaft of the linal selector continues in its upward moven'ient the shaft wiper Q20 engages an insulating portion oit commutator segment 221, whereupon the previously traced energizingl circuit ot relay 151 is opened at shaft wiper 220 and relay 151 energizes in` the opposite direction to retract its armature, reestablishing the shunt around the intermediate winding o relay 106, whereupon the current tlowing over the fundamental circuit again increased to its normal value and stepping relay 114 again energizes. In this manner during the upward movement of the switch shaft 21S, polarized relay 151 is intermittently operated to thereby deenergize and energize the sender stepping relay 114 until the oilice sender is satisfied with respect to its hundreds or final brush selec-tion setting when the No. 0 counting relay 112 becomes energized to open the fundamental circuit.

It is to be noted in connection with the operation of relay 151 that this relay being polarized. responds very quickly when current flows through its winding in one direction by reason ot a circuit through the shaft wiper 220 of thc final selector switch and also when this circuit is opened at the shatt wiper of the switch, and that therefore the pulses transmitted from the final selector switch are repeated to the ollice sender with out appreciable delay.

As soon following the opening ol' the itundamental circuit at the oliice sender as the shaft wiper Q20 engages the next insulating portion of the commutator segment 221, thereby opening the circuit of polarized relay 151, the line relay 106 deenergized to open the previously traced circuit extending through the winding of relay 204- at the linal selector switch and relay 2011 thereupon de.- cnergized to arrest the upward movement ot the switch shaft. It is to be noted that relay 106 is prepared for releasing` immediately Iupon the opening of the fundamental circuit at the sender regardless ot the position of relay 151 as determined by the commutator o't the final selector. It relay 151 has retracted its armature, relay 106 releases quickly since only its low resistance winding is connected to the fundamental circuit at this time. If the armature of relay 151 is attracted, the intermediate and right-hand high resistance windings oi relay 106 are connected in opposition through the front contact of polarized relay 151, and the cable capacity in the interotlice trunk is thereby permitted to charge very quickly through the windings oit relay 106 as soon as the lnndamental, circuit is opened at the sender, and the low resistance shunt is removed from around the differential winding ot the relay. Upon the deenergization ot relay 20st, scquence switch 203 is advanced into position 3 over a circuit which may be traced from battery, through the magnet winding of scquence switch 203, the upper contacts otI cam 224., the lett-hand armature and back coutact vof relay 204, and thence to ground at the upper contact ol cam Q11, lVith scquencc switch 203 in position 3, the previously traced circuit extending through the windings of relays 20st and 151 is again established and relay 204 upon energizingl advances the sequence switch 203 into position 1l. lilith sequence switch 203 in position 4t, the final selector switch is controlled in the manner previously described in its group selection movement. Inasmuch as the Final selector switch functions duringits group selec tion movement in the well known manner, its operation will not be described in detail herein. The control of the final selector switch in .its group selection movement, however. is more critical than its control duringr its brush selection movement, since the holding notches in the lower portion ot the switch shaft Q16 are more closely spaced and consequently any over-running of the switch shaft is more vital. To permit an earlier closing' of the circuit ot' relay 151, the conducting portions ot the group selection segment 223 ot' the switch commutator, are widened downwardly. the upper edges of these conducting portions are maintained in the usual position relative to the wiper 226 to insure the switch against under-running.

Following the group selection or tens selection movement of the final selector the sequence switch 20S advances in the well known manner into position 6, in which position the final or units selection movement otl the switch shaft is controlled. This operation oit the linal selector switch and the subsequent functioning ot the switch to test the called line, proceeds in the well known manner.

Following the units selection movement of the final selector switch., sequence switcl 203 is advanced out ot' position 8, whereupon the previously traced holding circuit of relay 191 is opened at the contact ot cam 202. .llelay 121 upon deenergizing closes at its lett-hand armature and back contact a circuit for advancing sequence switch 123 out ot' position 8 and into position 9. lilith sequence switch 123 in position 9, a circuit is established through the lett hand winding ot line relay 106 and the control circuit otiice sender :tor causing the advance ot' the otlice sender tor talking selec-tion in the manner fully set forth in the aforesaid patent to F. A. Stearn and l". J. Scudde-r. This circuit may be traced from battery, through the lower contact of cam 105, (0 to 4t), resistance element 133, the left-'hand winding of relay 10G, the upper right-hand contact of cam 107 (9 to 10) thence as previously traced through the oliice sender and returning over terminal 108 to ground at the lower left-hand. Contact of cam 14:0 (9 'to 10). ltelay 10G energizes in this circuit and at its armature and front contact closes the previously traced circuit for relay 121, which` upon energizing closes a circuit for advancing sequence switch out of position 9 and into position 10.

Following talking selection the circuit for relay 106 is opened and relay 121 deenergizes advancing sequence switch 123 into position 11. Vith sequence switch 12B in position 11 a circuit is established over the interoflice trunk in t-he well lnown manner, through the lower right-hand contact of cani 140 (11 to 18) through the winding of relay 152, and the upper right-hand contact of cam 119, and relay 152 upon energizing establishes a circuit for relay 121 which may ybe traced from battery', through the left-hand winding of relay 121, and thence to ground at the armature and contact of relay 152. Relay 121 upon energizing closes a circuit for advancing sequence switch 1223 out of position 11 and into the talking position 16. Inasmuch as the operation of applying ringing current to the line of the calledsubscriber is well known in the art, and since it is immaterial to an understanding of this invention, the ringing circuits associated with the incoming selector have not been disclosed or described herein.

Following the termination of the conversation between the calling and called subscribers, the calling subscriber restores his receiver to its switch-hook whereupon the line switch 100 and district selector switch 10.1 become restored in the well known manner. Upon the restoration of switch 101, the circuit of relay 152 is opened which in turn opens the circuit of relay 121. Relay 121 upon deenergizing closes at its left-hand armature and back contact the previously traced circuit for advancing sequence switch 12? out of position 1G into position 18. lilith` sequence switch 123 in position 1S a circuit is closed for the down-drive magnet '15B which may be traced from battery, through the magnet winding the lower lefthand and` upper right-hand contacts of cam 122, and thence to ground through the lefthand contacts of cam 137. Magnet 153 upon its energization presses the depending portion of the switch shaft against the constantly rotating down-drive drum 154, whereby the switch shaft is moved downwardly into its normal position. Upon reaching its normal position a circuit is closed for advancing sequence switch 123 into ,its normal position over a circuit which may 'be traced from. battery, through the magnet winding of sequence switch 123, the contact of cam 155 (17 to 8), normal coinmutator segment 150, shaft wiper 13S and thence to ground` at the contact of cam 157 (i to 1).

zis soon as sequence switch 123 leave-s position 10%, the circuit previously traced for maintaining relay 209 of the linal sclcctor switch energized, is opened at cam 13T and the restoration of the final selector switch is thereupon initiated. The final selector switch thereupon restores to normal position in the manner fully set forth in the aforesaid application. All of the circuits employed in the establishment of the connection are now in their normal condition.

That is claimed is:

1. In a telephone exchange system, a calling line, selector switches and a connecting' circuit for extending a connection from said line, a sending mechanism for controlling said switches, a fundamental switch controlling circiuit comprising said connecting circuit extending between said sending mechanism and said switches, means associated with one of said switches controllable over said fundamental circuit for governing the extent of movement of said switch, and means operative during` the movement of said switch for revertively controlling' said sending mechanism, said lirst named means being rendered quick to release over a fundamental circuit of upwards of fifteen miles in length when a releasing` condition is established in said circuit at said sending mechanism.

2. In a telephone exchange system, a calling line, selective switches and a connecting circuit for extending a connection from said line, a sending mechanism for controlling said switches, a fundamental switch controlling circuit con'iprising said connecting circuit extending between said sending mechanism and said switches, a line relay associated with one of said switches controllable over said fundamental circuit, a control relay under the control of said line relay for governing the extent of movement of said switch, and means operative during the movement of said switch for revertively controlling said sending mechanism.

3. In a telephone exchange system, a calling line, selector switches and a vconnecting circuit for extending a connection from said line, a sending mechanism for controlling said switches, a fundamental switch controlling circuit comprising said connecting circuit extending between said sending mechanism and said switches control means at said sending mechanism, and a line relay associated with one of said switches controllable over said fundamental circuit, a control relay under the control otI said line relay tor governing the extent of movement ot said switch, and means operative during the movement ot said switch it'or intermittently operating said control means.

Ll. In a'telephone exchange system, a calling line, selector switches and a connecting circuit for extending a connection trom said line, a sending n'iechanisln for controlling said switches. a fundamental switch controlling circuit comprising said connectcircuit extending between said sending mechanism and said switches, control means at said sending mechanism and a line relay associated with one ot said switches controllable over said fundamental circuit, means under the control o't said line relay for governing the extent ot movement of said switch, means operative during the movement ol said switch tor intermittently operating the control means at said sending mechanism, and means also operative during the movement oif said switch to maintain said switch controlling means operated until said switch completes its selective move.- ment.

5. In a telephone exchange system, a calling line, selector switches and a connecting circuit 'for extending a connection from said line, a sending mechanism for controlling said switches, a fundamental switch controlling circuit comprising said connecting circuit extending between said sending mechanism and said switches, a stepping relay at said sending mechanism and a line relay associated with one ot said switches controllable over said fundamental circuit, a control relay under the control of said line relay tor governing the extent ot movement ot' said switch, means operative during the movement of said switch `for intermittently operating said stepping relay, and means also operative during the movement of said switch to maintain said control relay operated until said switch completes its selective movement.

(i. In a telephone exchange system, a calling line, selector switches and a connecting circuit for extending` a connection from said line, a sending mechanism for controlling said switches, a Yfundamental switch controlling circuit comprising said connecting circuit extending between said sending mechanism and said switches, a stepping relay at said sending mechanism, and a line relay associated with one ot said switches controllable over said fundamental circuit, a control relay under the control ot said line relay for governing the extent of movement of said switch, a commutator for said switch, a wiper for engagement with said commutator during the movement of said switch for intermittently shunting said stepping relay, and a second wiper for engagement with said commutator to maintain said control relay operated until said switch completes its selective movement.

7. Ina telephone exchange system, a calling line, a selector switch, another selector switch and a connecting circuit: tor extending connection from said line. a switch controlling circuit including` said connecting circuit extending to said first named switch, a second control circuit extendingl between said switches, means at said first named switch for repeatinj control impulses irom said first named controlling circuit to said last named control circuit, said means being quick to release over a switch controlling circuit of upwards ot fifteen miles in length when a releasing condition is established in said circuit and means at said first named switch for repeating revertive impulses from said last named control circuit to said first named controlling circuit.

8. In a telephone exchange system, a calling line, a selector switch, another selector switch and a connecting circuit tor extending a connection 'from said line, a sending` mechanism for controlling said switches, a fundamental switch controlling circuit extending between said sending mechanism and said first named switch, a control circuit extending between said switches, means at said first named switch for repeating control impulses from said fundamental circuit to said control circuit, said means being rendered quick to release over a fundamental circuit ot upwards of fitteen miles in length when a releasing condition is established at said sending mechanism and means at said first named switch tor repeating revertive impulses 'from said control circuit to said fundamental circuit :tor controlling said sending mechanism.

9. In a telephone exchange system, a calling linel` a selector switch, another selector switch and a connecting circuit for extending a connection from said line, a sending mechanism for controlling said switches, a fundamental switch controlling circuit extending between said sending mechanism and said first named switch, a line relay associated with said first named switch controllable over said fundamental circuit, a control circuit extending to said other switch and controlled by said line relay, said means being rendered quick to release over a fundamental circuit ot upwards of fifteen miles in length when a releasing condition is established at said sending mechanism, a switch controlling relay at said other switch and a pulsing relay at said first named switch in said control circuit, means at said other switch operative during the movement thereoi:l for transmitting imgulses to said pulsing relay, and means controlled by said pulsing relay for revertively controlling said sending mechanism.

10. ln a telephone exchange system, a calling line, a first selector, a final selector and a connecting circuit for extending a connection from said line, a sending mechanism for controlling said switches. a fundamental switch controlling circuit extending between said sending mechanism and said first selector, a line relay associated with said first selector controllable over said fundamental circuit, said means being rendered quick to release over a fundamental circuit of upwards oit' fifteen miles in length when a releasing condition is established at said sending mechanism a control circuit extending to said final selector and controlled by said line relay, a switch controlling relay at said final selector and a pulsing relay at said first selector in said control circuit, means at said final selector operative during the movement thereof for transmitting impulses to said pulsing relay, and means controlled by said pulsing relay for revertively controllingsaid sending mechanism. l

11. In a telephone exchange system, a calling line, a first selector, a final selector and a connecting circuit for extending a connection from said line, a sending mechanism for controlling said switches, a fundamental switch controlling circuit extending between said sending mechanism and said first selector, a line relay associated with said first selector controllable over said fundamental circuit, a control circuit extending to said final selector and controlled by said line relay, a switch controlling relay at said final selector and a polarized pulsing relay at said first selector in said control circuit, means at said final selector operative during the movement of said final selector for transmitting impulses to said pulsing relay, and means controlled by said pulsing relay for revertively controlling said sending mechanism.

12. In a telephone exchange system, a calling line, a first selector, a final selector and a connecting circuit for extending a connection from said line, a sending mechanism for controlling said switch, a fundamental switch controlling circuit comprising said connecting circuit extending between said sending mechanism and said first selector, a stepping relay at said sending mechanism and a line relay associated with said first selector controllable over said fimdamental circuit, said line relay being rendered quick-to-release over a fundamental circuit of considerable length when a releasing condition is established at said sending mechanism, a control circuit extending to said final selector and controlled by said line relay, a switch controlling relay at said final selector, and a pulsing relay at said first selector in said control circuit, means at said final selector operating during the movement thereof' for transmitting impulses to said pulsing relay, and means controlled by said pulsing relay for intermittently altering the resistance of said fundamental circuit for operating said stepping relay.

13. In a telephone exchange system, a calling line, a rst selector, a final selector, and a connecting circuit for extending a connection from said line, a sending mechanism for controlling said switches, a fundamental switch controlling circuit comprising said connecting circuit extending between said sending mechanism and said first selector, a stepping relay at said sending' mechanism and a line relay associated with said first selector controllable over said fundamental circuit, said line relay having a low resistance operating winding and a normally shunted high resistance winding, a control circuit extending to said final selector and controlled by said line relay, a pulsing relay in said control circuit, and means under the control of said pulsing relay for removing the shunt from said high resistance winding whereby said stepping relay is intermittently operated.

14. In a telephone exchange system,a calling line, a first selector, a nal selector and a connecting circuit for extending a connection from said line, a sending mechanism for controlling said switches, a fundamental switch controlling circuit comprising said connecting circuit extending between said sending mechanism and said first selector, a stepping relay at said sending mechanism and a line relay associated with said first selector controllable over said fundamental circuit, said line relay having a low resistance operating winding, a normally shunted high resistance winding and a differential winding, a control circuit extending to said final selector controlled by said line relay, a pulsing relay in said control circuit, and means under the control of said pulsing relay for removing the shunt from said high resistance winding whereby said stepping relay is intermittently operated and for associating said differential winding with said fundamental circuit.

15. In a telephone exchange system, a calling line, a selector switch and a connecting circuit for extending a connection from said line, a sending mechanism for controlling said switches, a. fundamental switch controlling circuit comprising said connecting circuit extending between said sending mechanism and said switch, a stepping relay at said sending mechanism and a line relay associated with said switch controllable over said circuit, said line relay having a low resistance operating winding, a normally shunted high resistance winding and a differential winding, means at said sending mechanism for opening said circuit, and means at said switch Jfor alternately removing the shunt from said high resistance winding and for associating said dierential winding .with said circuit whereby the resistance of said circuit is intermittently increased to operate said stepping relay and whereby said line relay is rendered quick to release upon the opening of said circuit at said sending mechanism.

16. In a telephone exchange system, a call ing line, a selector switch for 'egite'nding a connection from said line, a coiiti'ol relay for said switch, an operating circuit for said relay, said relay having a low resistance operating winding, a normally shunted high resistance winding and a diii'erential winding, and means at said switch for alternately removing the shunt from said high resistance winding and for associating said differential winding with said operating circuit whereby said low resistance and high resistance windings are connected cumulatively in series in said operating circuit and whereby said differential winding is connected in series with said high resistance winding and in opposition to both of said other windings.

17. In a telephone exchange system, a calling line, a selector switch Jfor extending a connection from said line, a control relay for said switch, an operating circuit for said relay, said relay havingan operating winding and a differential winding, and means at said switch for intermittently rendering said diii'erential winding effective whereby said relay is rendered quick to release'upon the opening of said operating circuit.

18. The method of stopping an automatic switch at a desired position which switch is controlled from a distant control point over a cable loop, which consists in transmitting progress impulses from said switch to the control point, transmitting a stopping order from the control point to said switch early enough to allow for the greatest lag of a long cable, rendering the controlling means of said switch sensitive to said stop order and insuring the movement of the switch to the desired position independent of the controlling means.

19. The method oi" stopping an automatic switch at a desired position which switch. is controlled from a distant control point over a cable loop, which consists in transmitting progress impulses from said switch to the control point, transmitting a stopping order from the control point to said switch early enough to allow for the greatest lag of a long cable, rendering the controlling means oi2 said switch sensitive to said stop order and insuring the movement of the switch to the desired position if the stop order arrives before the switch has reached the desired position.

In witness whereof, I hereunto subscribe my name this 28th day "of December A. D.,

LEWIS II. JOHNSON. 

